The present invention relates to a device comprising a plurality of fluid elements arranged in a matrix configuration, the level of fluid in each element being controllable by means of an electric force, which device is further provided with:
first means for applying an electric force to a number of selected elements in one or more of the rows of fluid elements;
second means for applying an electric force to a number of selected elements in one or more of the columns of fluid elements;
such that the fluid level rises in the selected elements to which an electric force is applied by both the first means and the second means; and
memory means for retaining the risen level in the selected elements.
Such a device is known from the international patent application WO 98/51509, which particularly refers to the delivery of fluids to a receptor, e.g. delivery of pigments to a printing media.
The known device uses matrix addressing to control the level of fluid in the fluid elements thereby advantageously reducing the number of drivers necessary to set the fluid level in the different elements.
The invention aims at providing a device of the type described above, which is particularly suited for manipulating the level of fluid in the fluid elements in a precise way without the need for extra components.
The device according to the invention is characterized in that the fluid elements comprise capillary tubes which are arranged such that the level of fluid is controllable while exercising a threshold like behaviour.
By designing the capillary tubes such that the physical characteristics thereof induce the threshold like behavior extra components, such as transistors or diodes, become redundant. This greatly reduces the size of the device according to the invention, which is an important advantage in the relevant technical fields.
According to a first preferred embodiment of the device according to the invention the capillary tubes comprise electrodes which are arranged inside the capillary tubes. Preferably the electrodes comprise a coating layer of an electrically conducting material.
It is noted that in U.S. Pat. No. 5,666,396 by the same applicant an X-ray examination device is described which is provided with an X-ray filter comprising a matrix of capillary tubes provided with electrodes comprising a coating layer of an electrically conducting material. The level of X-ray absorbing fluid inside the capillary tubes is controllable by means of application of an electric force to a number of selected capillary tubes. Thin film transistors are used to induce a threshold like behaviour for the fluid rise inside the capillary tubes, which is what the invention aims to overcome.
According to a second preferred embodiment of the device according to the invention the electrodes are divided into segments in longitudinal direction of the capillary tubes. In addition or as an alternative thereto the electrodes are divided into segments in transverse direction of the capillary tubes. Dividing the electrodes into segments thereby introducing a gap is an elegant construction which inherently induces the desired threshold like behaviour for the fluid rise. Preferably one or more of the electrode segments are coupled to the first means, leading to the so called xe2x80x98liquid/in-capillary electrode embodiment. According to an alternative embodiment one or more of the remaining electrode segments are coupled to the second means, leading to the so called xe2x80x98in-capillary/in-capillaryxe2x80x99 electrode embodiment.
According to a still further preferred embodiment one or more of the electrode segments are coupled to the memory means. A memory effect can be obtained by adding an extra electrode to a capillary tube. In conformance with the embodiments described above an electrode segment can serve as the extra electrode.
The invention also refers to an X-ray filter comprising a device according to the invention, wherein the capillary tubes are filled with an X-ray absorbing fluid.
Furthermore the invention refers to an X-ray examination device comprising an X-ray filter according to the invention.
The invention also refers to a microfluidic chip comprising a device according to the invention. Microfluidic chips as such are known from a publication in SCIENCE Vol 282, p. 399 and comprise a system of capillary channels, wherein, for example, a reactive is being transported. These microfluidic chips are applied in the field of biochemistry, for example to perform a DNA sequencing. Microfluidic chips can be also applied in the field of chemistry, for example for the purpose of chemical analysis.